[Cryptography] Literature on reusing same key for AES / HMAC?

[Tony Arcieri]

On Wed, Nov 4, 2015 at 11:09 AM, Will Sargent <will.sargent at gmail.com>
wrote:

> "With HMAC vs AES, no such interference is known. The *general feeling* of
> cryptographers is that AES and SHA-1 (or SHA-256) are "sufficiently
> different" that there should be no practical issue with using the same key
> for AES and HMAC/SHA-1."
>

In general I would say using a secret value as a key for a cipher (a PRP in
the case of AES) in addition to an unrelated PRF should be fine and have
seen several constructions of this nature.

For what it's worth, Ruby on Rails "Message Encryptor" class reuses the key
this way by default.

But perhaps I'm naive and mistaken!

-- 
Tony Arcieri
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